Traffic control systems are ubiquitous in modern transportation systems. Traffic control systems are commonly used to regulate the flow of motorized vehicles, non-motorized vehicles and pedestrians on roads, streets, highways, bridges, and other surface transportation media designated for such purposes. Henceforth, the term “roadway” will be used to include any surface transportation media. Traffic control systems use visible indicators to direct when travel is permitted or not permitted on designated roadways. The purpose of traffic control systems is to provide safe and efficient access to the shared roadway for a specified group of roadway users. Crosswalks are portions of the roadway that are allocated for pedestrians to cross one or more roadways. They are identified by painted markings on the roadways and/or signage on the side of the roadway as described in the Manual for Uniform Traffic Controller Devices (MUTCD) which is available at http://mutcd.fhwa.dot.gov/htm/2003r1r2/html_index.htm.
A traffic control system is comprised of an electronic device that determines which vehicle and pedestrian signals are to be active to control movements through a designated portion of the roadway. As used herein, an intersection refers to the intersection of two or more roadways that share a common right of way in such a manner that one or more traffic movements must be constrained to avoid conflicts that may result in collisions. A signalized intersection is an intersection that uses a traffic control system to control vehicle and pedestrian movements at an intersection or on a roadway. The traffic control system may incorporate sensors that detect the presence of vehicles at specific places in the roadway. The traffic control system may also have detectors to sense when pedestrians press a button that signifies that they are requesting (calling for) service to be able to cross a specific element of the roadway.
Many traffic control systems provide control of pedestrian movements using visible and audible messages and/or symbols. According to the MUTCD, visible signals used to control pedestrian movements include illuminated signals that display the words “WALK”, “DON'T WALK”, and “WAIT.” Other traffic control systems use the illuminated symbol of a walking person in lieu of a “WALK” signal and a symbol of a hand in lieu of the “DON'T WALK” or “WAIT” signals. Some traffic control systems also include countdown timers that display the number of seconds remaining before the pedestrian is to be clear of the segment of the roadway shared with other users. In addition to the visible displays, some traffic control systems also broadcast audible messages in the form of verbal phrases or easily differentiable tones such as chirps and coo-coos that mimic bird calls.
Pedestrian movements at signalized intersections are controlled by displaying the “WALK” indication indicating that individuals should proceed to cross the designated roadway with due caution. The “WALK” display changes to a flashing “DON'T WALK” indicating that a pedestrian who is not already in the roadway should no longer leave the curb and enter the roadway. A non-flashing “DON'T WALK” display indicates to the pedestrian it is no longer safe to be in the roadway for the designated crossing.
Some pedestrian movements are controlled by the traffic controller that automatically allocates a regular fixed time interval for pedestrian crossings and requires no action by the pedestrian to register a request for service with the traffic controller. Some traffic control systems provide a sequence of displays to both vehicles and pedestrians when triggered by manual push buttons, or other pedestrian friendly features. Usually the push buttons that are used by the pedestrian to register a request for service with the traffic controller are physically positioned in the proximity of the side of the roadway adjacent to the media used by motorized vehicles. The MUTCD gives guidelines as to the placement and orientation of the pedestrian activation buttons. However, variations of roadway geometries preclude consistent and predictable placement of the pedestrian call buttons at many signalized intersections.
The operation of today's traffic control systems provide a reasonable degree of safety provided that pedestrians and vehicle operators use their sight to identify potential hazards and conflicts as well as to correctly identify the signal lights that are illuminated to control their movements. Pedestrians with cognitive and visual acuity impairments must rely on auditory cues to assist them in lieu of visual signals. The difficulties of crossing a roadway for people with cognitive and vision impairments are described in detail in Harkey et al., “Accessible Pedestrian Signals: A Guide to Best Practices” (hereinafter “Harkey”) available at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w117a.pdf. Harkey's Appendix D (also available at http://www.walkinginfo.org/aps/appendix_d_understanding.cfm) discusses the safety and access difficulties faced by blind pedestrians. Both of these are incorporated herein by reference. Some of these difficulties are described below.
As described by Harkey, blind or visually impaired pedestrians typically travel and cross streets using human or dog guides, using long, white canes to identify and avoid obstacles, using special optical or electronic aids, or using no additional aids. In any case, according to Harkey, street crossing comprises a number of tasks that are summarized briefly below.
First, the pedestrian must determine that she has arrived at a street, typically based on one or more factors such as curb locations, ramps, traffic noise, or audible signals. Second, the pedestrian must identify the street. Streets signs are generally not helpful, and location information is usually not provided in a manner suitable for the blind. Thus, blind pedestrians often count the number of blocks and street crossings they have traveled, or ask bystanders for assistance in identifying a street crossing. Third, the blind pedestrian must assess the street/intersection configuration including such characteristics as crosswalk locations, numbers and widths of streets, presence of medians or islands, locations and availability of pedestrian push buttons, and orientations of intersection corners. While traffic noise can be helpful, traffic noise provides limited assistance, and available pedestrian push buttons may not be readily located by the blind pedestrian. Fourth, based on the configuration of the intersection, the blind pedestrian crosses based on alignment with respect to a target location on an opposite side of the roadway, activation of a pedestrian push button, and a beginning of a crossing time in response to push button activation. In some cases, traffic noise parallel to an intended direction is used as an indication that the blind pedestrian can begin to cross. This traffic noise can be helpful in establishing a proper orientation during crossing, but can be misleading as well. For example, noise associated with turning vehicles can make alignment more difficult. Typical crossing difficulties include finding and activating a crossing pushbutton—the time required to do this may seriously reduce the time available for the actual crossing. Moreover, in the absence of traffic, it may be impossible to determine that a walk interval established by a walk signal has begun or ended. In some locations, walk intervals are too short, or pedestrian push buttons are not provided or are too difficult to access. Even if a lengthy walk interval is provided, traffic often continues to flow during at least a portion of the walk time.
For the reasons identified above and other safety and access reasons, improved traffic control devices and methods are needed.